The price increases can be particularly alarming considering families on average spend approximately 6.6% of their household income on food and 43% of those expenditures on food away from the home, according to the US Department of Agriculture. Rising food prices can affect families from all demographics but especially those in low-income situations.

Why food prices rise

There are many reasons behind price changes that may not seem obvious.

"The biggest drivers of rapid increases in prices tends to be weather-related events," says Greg Colson, an associate professor of agriculture and applied economics at the University of Georgia. "So it's droughts, it's floods, particularly droughts recently, that tend to drive very rapid increases."

Another important thing to note is that food prices on average, including the price of eggs and poultry, actually dropped back in 2016, by an average of 1.3%. Also in 2016, retail egg prices declined 21.1% as egg-laying flocks recovered from the Highly Pathogenic Avian Influenza outbreak.

The number of animals in both dairy and poultry sectors also increased, leading to decreasing prices in 2016. These trends continued into 2017, which makes the rising food prices of 2018 seem surprising. But it may just be the market leveling out.

"There's a seasonality, a cycle to all this, it's tough (to forecast) because in general forecasting we're looking at averages, or we've got trends or cycles, it's easy, but forecasting shocks is very hard," Colson says. "Nor can you predict, is it going to be a minor or a major drought next year?"

When experts forecast prices, they look at averages and use trends or cycles, but forecasting shocks is tough to do, Colson said. Experts can't predict whether there will be a drought next year, and if there is a drought, they also can't predict how severe it will be.

Food-at-home prices are typically more volatile than food-away-from-home prices, according to the USDA, because the cost of dining out reflects more than the price of food. In fact, food-away-from-home prices rose an average of 2.6% in 2016, while food-at-home prices fell 1.3% — the first time such prices have declined since 1967. While eating at home has long been considered a more affordable choice, that was especially true in 2016.

Costs associated with food service such as wages and benefits have been increasing and are potentially partially responsible for the percentage differences in rising costs. For example, when prices at Dunkin' Donuts stores rose in 2016, Dunkin' CEO Nigel Travis told investors this was due more to changes in minimum-wage requirements than to commodity pricing.

How outside factors affect food prices

Being aware of which external factors affect food prices and how can help you make sense of how and when you'll see these changes.

For example, fuel prices and commodity costs can affect what you see on the price tag. Lower fuel prices don't just affect your gas tank; they also make food prices lower, as transportation costs for commodity goods as well as for distribution make it cheaper for producers. And in 2017, the USDA said there were more egg-laying birds, which helped drive down the cost of eggs.

"There's a lot of moving parts," Colson says. "And so even if there's no magical events in the US, if there's positive/negative shocks elsewhere around the world, it can leave a big impact on the market."

In the third quarter of 2017, spending at restaurants and other eateries increased 2% from the same time last year, according to NPD Group, a market-research company. NPD Group attributed most of that increase to rising menu prices.

Though food prices are expected to rise in 2018 because of numerous variables, there's no need to panic when planning out the monthly grocery budget. Because of deflation in 2016 and the first half of 2017, 2018 prices are expected to stay below 2015 prices, according to the USDA.